1. Field of the Invention
Exemplary aspects of the present invention generally relate to an optical scanning device employed in a writing system in an image forming apparatus such as a digital copier and a laser printer, and an image forming apparatus including the optical scanning device.
2. Description of the Background
Related-art image forming apparatuses, such as a copier, a facsimile machine, a printer, or a multifunction printer having two or more of copying, printing, scanning, and facsimile functions, form a toner image on a recording medium (e.g., a sheet) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image bearing member (e.g., a photoconductor); an optical scanning device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; the electrostatic latent image is developed with a developer (e.g., a toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
As described above, the image forming apparatus such as a laser printer, a digital copier, or a laser facsimile machine includes the optical scanning device to form the electrostatic latent image on the surface of the photoconductor. One example of the optical scanning device is configured to deflect a light beam emitted from a light source using a rotating deflector to scan the surface of the photoconductor with the deflected light beam.
To meet demand for high-quality images and high-speed image formation, a tandem-type image forming apparatus using multiple photoconductors is widely used as a full-color image forming apparatus in recent years. In the tandem-type image forming apparatus, higher accuracy in superposition of images respectively formed on the multiple photoconductors is required to achieve the high-quality images.
However, the above-described optical scanning device using the rotating deflector is susceptible to vibration due to high-speed rotation of a polygon mirror, possibly resulting in image deterioration such as color shift and uneven image density.
To prevent such image deterioration caused by the vibration from the optical scanning device, various methods and techniques have been proposed.
Published unexamined Japanese Patent Application No. (hereinafter referred to as JP-A-) 2006-323066 discloses an image forming system in which a vibration damping means is included in an optical scanning device to suppress vibration.
In another approach, JP-A-2002-341467 discloses an optical scanning device configured to suppress generation of vibration using a compact and lightweight configuration.
However, the image forming system disclosed in JP-A-2006-323066 requires higher cost to include the vibration unit and multiple detectors. Further, although a method for suppressing transmission of the vibration by improving rigidity of the optical scanning device is disclosed in JP-A-2002-341467, the range of available layouts of the optical scanning device is more limited because the optical scanning device needs to be fixed to a main frame of an image forming apparatus.
In the tandem-type image forming apparatus, in general, multiple optical scanning devices are included to perform exposure on multiple photoconductors. Alternatively, a single optical scanning device may be used to perform exposure on multiple photoconductors. When the single optical scanning device is used to emit four light beams onto surfaces of four photoconductors, for example, four optical paths are formed using multiple reflecting mirrors provided in the optical scanning device. A wide variety of arrangements of the reflecting mirrors is available depending on the layout of components in the image forming apparatus. To achieve such a wide variety of arrangements, one example of the optical scanning device includes a first optical housing and a second optical housing, with a rotating deflector, and an optical element such as a lens when needed, included in the first of these two optical housings while the multiple reflecting mirrors are included in the second optical housing.
However, as described above, in the optical scanning device using the rotating deflector, the polygon mirror is rotated at high speed and vibration is transmitted from the optical housing including the rotating deflector to the other optical housing. Consequently, portions of the other optical housing cantilevered to the image forming apparatus are heavily susceptible to vibration, resulting in image deterioration.